New protocol decoder: wiegand

libsigrokdecode recently gained support for yet another protocol decoder: wiegand.

This PD supports the Wiegand interface protocol, often used in electronic entry systems, card swipe systems, some RFID systems and such.

As usual, we have a bunch of example files in the sigrok-dumps repository, and a few test-cases in the sigrok-test repo.

The decoder was contributed by Sean Burford, thanks a lot!